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  • exhaust heat

    Hello,

    Maybe this is a nonsense, but has anybody tried to use the heat from the exaust pipe to heat up the oil? This would allow very quick change over.
    I know the manifold would be way too hot, but perhaps there is a point down the pipe in which temperatures are adequate.
    Veggy oil self ignites at around 250 degrees, I think.

    Regards
    gonzalo

  • #2
    Re: exhaust heat

    Hi,

    There was a brief discussion here a while back but I can't find it. I was thinking along similar lines for the two tankers; faster heating and quicker change over. I think we came to the conclusion that in Oz we would run foul of the ADR's (Australian Design Rules) void insurances and be illegal etc.

    I thought of running a fuel line attached parallel to the exhaust manifold for a short distance (300mm or so) and then insulated line to the IP. One issue would be at shut down the oil would sit, not moving, and heat up to possibly dangerous levels - no obvious solution to this. Another issue is the oil would be cold from the exhaust to the IP at start up, solvable with a veggie therm or similar. As you say, very simple and no water plumbing involved.

    I thought the flash point of oils was higher 450 - 800 degrees C ?? but perhaps that was a US site and they were talking Fahrenheit? Anyway if you decide to give it a go, keep us posted.

    cheers, Michael

    Comment


    • #3
      Re: exhaust heat

      While exhaust heat is certainly a possibility to get to a workable arrangement, I believe it is too much trouble for too little benefit.

      On my 300D and others I know of, it only takes a few Km for the engine coolant to come up to temp. I would suggest other vehicles would do similar given properly fuctioning thermostats. This being the case, how much fuel would one save if they could change over faster? 1 liter? 1/2?

      The savings would then have to be compared against the cost of getting an exhaust HE to a workable and safe level. Having looked into this myself, I believe it would neither be a cheap or very practical idea. The engineering hurdles of the space limitations especially if one were looking to do this to a reasonable modern compact type car would also make this a questionable endeavor.

      One other thing that I think would be a fundamental flaw in this idea would be that you are putting the cart before the horse in what was warming up first. You could get the fuel hotter than the engine a lot quicker but then you come back to trying to inject hot oil into a cold-er engine.

      I believe that the oil will only inject probably a few degrees above engine temp and even if one was to believe the fuel went in at full heated temp, no one would deny that the cylinder walls and other combustion chamber surfaces would still be way below operating temperature making a perfect enviroment for the formation of deposits and the possibility of ring coking, valve sticking, injector fouling and the like.

      It is generally accepted that the engine should be hot as well as the fuel when using veggie. It would seem to be a good move to pay the small price to burn some start up fuel in order to prevent major expensive repairs by trying to get a bit too penny pinching and "cheat" the warm up time an engine needs to work successfully on veg.

      If one were looking to warm up the fuel tank in a very cold enviroment, exhaust heat may be a worth while solution.

      For start up's, I think paticence would be a virtue very well rewarded in the long run.

      Comment


      • #4
        Re: exhaust heat

        It's not about saving money on switching over.

        It's about heating the oil to the only peer reviewed safe temperature of 150 degrees Celsius according to the journey to forever site.

        I was thinking of a hose in hose system on the exhaust.

        Exhaust temps are hotter than 150c but does that matter?
        Converted 97 dodge Ram
        www.veggiescout.blogspot.com

        Comment


        • #5
          Re: exhaust heat

          Probably the best way to tap the heat from the exhaust would be a thermosyphon containing coolant. You could have it circulating with a small pump, but it should not be necessary as physics could do all the work without the aid of a pump, providing your tank is above the exhaust. When you shut down the engine it would continue to circulate on the residual exhaust heat so that the heat in the veg oil would not spike to dangerous levels as it would if you were running the fuel line along the exhaust (not recommended!).

          This heat could be accessed via a heat exchanger in the veg line or directly through a coil in the tank.

          It would be a quick way to heat a tank if you were running palm oil.
          Cheers
          Bruce


          1976 W123 300D (3 litre 5-cyl NA diesel running on SVO since June 2006)
          1982 W126 280SE (Sadly is For Sale)
          1993 W124 300D (3 litre 6-cyl NA diesel - being converted to SVO)

          Comment


          • #6
            Re: exhaust heat

            I'm surprised there hasn't been more discussion about head warmers. Perusing the diesel websites from the US seem to be on loads of engines. Are there any in australia? They just leave their car plugged in to a wall socket which keeps the heat preheated all night. Makes for easy starting in the morn.
            Joe Morgan
            Brisbane Biodiesel Site Admin
            http://www.brisbanebiodiesel.com

            Searching tips using Google - SVO Dual tank systems
            SVO, Common Rail and Direct Injection - Vehicles converted to Used Cooking Oil

            Comment


            • #7
              Re: exhaust heat

              Hi Joe,

              I have two 'block heaters'. The first one I brought is inserted though the side of the block into the water jacket, and looks like a small, squashed and bent hot water element. I haven't installed this one and may never, as it requires the removal of one of the severely rusted in plugs. It's 500 watt 120 volt.

              The second unit taps into the radiator hose, much easier to fit. The hose is cut and the unit acts as a joiner. It is also 120 volt and heats the block via convection currents. Diesel Giant sells these.

              I've seen electric elements that are inserted into the sump, some via the sump plug and others require a socket installed. These heat the sump oil directly. Most of this stuff has been developed for Canada and northern Europe. In Canada (eg. Edmonton) if you don't get to a city provided electric 'plug in' (bit like the old parking meters) in winter, you leave your car running or it's a tow away job after it's frozen solid.

              As an aside, during WW2 the German panzer tanks at the Russian front had fires lit under the sump region to enable starting. I know one of the boy soldiers whose job it was to gather the wood, light them, and keep them alive. Andreas was 15 at the time! At night they would also park trucks over any compost heaps they could find for the heat the heaps generated. At 15 and a half he was shot and repatriated to a recuperation hospital on the Italian / Austrian border where he saw out the rest of the war.

              cheers, Michael

              Comment


              • #8
                Re: exhaust heat

                The previous 2 posts have nothing to do with the topic, which is "exhaust heat".

                Block heaters have their place in preventing engine damage when vehicles are parked for extended periods and temps drop below zero, but these posts are off-topic and not related to utilizing heat from the exhaust.

                Maybe start a new topic and transfer these posts?
                Cheers
                Bruce


                1976 W123 300D (3 litre 5-cyl NA diesel running on SVO since June 2006)
                1982 W126 280SE (Sadly is For Sale)
                1993 W124 300D (3 litre 6-cyl NA diesel - being converted to SVO)

                Comment


                • #9
                  Re: exhaust heat

                  Also alittle of topic but still relates to heating your oil or in my case fat quicker.I am in the process of setting up a system to preheat the entire coolant system prior to start up.
                  Cheers Strawb

                  Comment


                  • #10
                    Re: exhaust heat

                    Don't sweat it Bruce, non linear logic solves more problems than any other.
                    cheers, Michael

                    Comment


                    • #11
                      Re: exhaust heat

                      I have been having a bit of a rethink about exhaust heat and how it could be used.
                      I still stand by the view that it is best to let the engine warm up for a longer time not the shortest before changing over to WVO and that the complexity of using exhaust heat as the main heat source would be overly complicated and costly as opposed to the more favoured coolant heating. Using exhaust heat to warm the oil in the tank and help thin it and melt any settled fats though does appear to have merit however.

                      I have noticed that the exhaust at the tailpipe is noticeably cooler that at the manifold and also convienently located near the fuel tanks. While the heat of the exhaust in this region is still a lot hotter than I would want 60L of oil I was carrying around to be, with a limited area of pickup, the oil would only ever be able to warm within some safe limits that could be regulated through the effectiveness of the heat exchanger.

                      If the pickup area on the exhaust was limited to an area that only allowed the oil to rise say 5-30o, then the problems of the oil overheating or burning would be eliminated and no other temp controls would be needed. The oil temp would certainly vary but as long as it was limited so as to get overly hot, there would be no problem.
                      I envisage routing the return line through the heated coil so oil was always flowing through it and would be sent to the tank nicely warmed.

                      I haven't measured the actual tailpipe gas temps but I suspect they could be relatively stable having been given time to cool somewhat along the length of the exhaust pipe which would itself act as a thremal mass to smooth out the highs and lows somewhat..

                      A limited heat pickup from the exhaust pipe such a a coil wraped around it or a length of pipe welded to it could work along the lines of sometimes being a little ineffective but never to overheat anything. A coil wrapped around the exhaust could be started to be on the long side and if too effective, could be easily shortened until a suitable temp over most normal driving conditions could be met.

                      The oil could easily be heated to 200oC without problem and given the small amount returned to the tank, even if the oil was heated to this level under unusual vehicle driving or loads, Unless the oil was overly heated to this level for a very long time. there would still be no problems.

                      Given the simplicity and very low cost of such a system, I think it could be worthwhile for those who would benifit from a bit of heat in their fuel tank.

                      Comment


                      • #12
                        Re: exhaust heat

                        David yes i too have wondered about useing all that wasted heat from the tail pipe, re heating the fuel tank, but have decided that its much much simpler to replace the 5/16 fuel line with a 1/2" line. problem solved as to sucking thick oil through a small tube, then deal with heating it in the engine bay with coolant.
                        all said and done i have wondered about heating the fuel on an air cooled motor and by whatever means[a couple of turns round the exhaust or in and out of the finning etc] is there an optimum temp to raise the fuel temp to.
                        i mean i am stuck on 80c [coolant] but would say 200c be beter if we could attain it reliably and constantly
                        ? is there a magic temp or a temp to be avoided ?
                        ? at what temp does wco have the same viscosity of dino
                        ?would we gain anything by going higher than this

                        Comment


                        • #13
                          Re: exhaust heat

                          Originally posted by dagwill View Post
                          ? is there a magic temp or a temp to be avoided ?
                          Yes, you should not exceed heating beyond the the flash point of any fuel that will enter your system. If you blend fuels or put additives into your fuel, then you have to consider what the flash point of the blend is. Consider change-over temps as well. For example, if using diesel as your start-up/shut down fuel, you need to consider that the flash point of diesel is around 80degC. But if you use Biodiesel, then the flashpoint is about 170degC. So you could heat more if you use bio for startup/shutdown.

                          Originally posted by dagwill View Post
                          ? at what temp does wco have the same viscosity of dino
                          It won’t. At best the viscosity of svos will be around 6 times higher than diesel


                          Originally posted by dagwill View Post
                          ?would we gain anything by going higher than this
                          If you mean higher than 200degC, then that is already way too high. As to a “benefit” it depends on how much insurance you have
                          Cheers
                          Bruce


                          1976 W123 300D (3 litre 5-cyl NA diesel running on SVO since June 2006)
                          1982 W126 280SE (Sadly is For Sale)
                          1993 W124 300D (3 litre 6-cyl NA diesel - being converted to SVO)

                          Comment

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